This proposal is to define the efficacy and mechanisms of avocado phytochemicals in inhibiting oral cancer development and modulation of related regulatory pathways in vivo. We hypothesize that avocado meat and its extracts prevent the formation of oral squamous cell carcinoma in vivo via a ROS-mediated mechanism based on our preliminary and published data. High basal levels of ROS have been found in premalignant and malignant mammalian cells including HPV- transformed primary, premalignant and malignant human oral cell lines. This is thought to be due to increased metabolic activity. However, increasing ROS levels from endogenous sources appears to be toxic to these cells. The D003 extract (chloroform fraction) isolated from avocado meat selectively enhances the levels of ROS and induces apoptosis in HPV-transformed primary, premalignant and malignant human oral cell lines but not normal primary cells. Our preliminary data also shows that whole avocado extract of avocado meat increases ROS levels and inhibits proliferation of the premalignant and malignant human oral epithelial cell lines. Freeze-dried avocado meat prevents DMBA-induced oral cancer formation in hamster cheek pouch model. We hypothesize that modulating ROS in vivo will lead to inhibition/prevention of oral cancer development. This hypothesis will be addressed in the hamster cheek pouch model with the following specific aims: i) Determine the ability of whole avocado meat and D003 extract to prevent the formation of oral tumors;ii) Investigate at the tissue and cellular level the role of intracellular ROS levels modified by avocado meat and D003 extract in the prevention of oral tumors in vivo. These studies will provide valuable information for future clinical trials. PUBLIC HEALTH RELEVANCE: This study will provide essential data establishing the scientific foundation for prevention of oral cancer by avocado fruit. These novel studies will be the first to examine the in vivo effect of avocado fruit on the prevention of oral cancer and molecular effects modified by avocado fruit on oral mucosa in pre-initiated oral tissues. The current study will provide a definitive assessment of the chemopreventive effects on oral cancer and the usefulness of the avocado fruit in future clinical trials for inhibition of premalignant and cancerous outcomes in high-risk populations.